Underground reservoirs of petroleum hydrocarbons are tapped by drilling wells from the earth's surface to penetrate, producing formations. Liquid hydrocarbons, or crude oil, may be forced to the earth's surface by formation pressure when a well is first drilled. However, when the formation pressure is insufficient to force the crude oil to the earth's surface, either due to an inherent low formation pressure or when a formation had been produced for an extended period of time such that its pressure has diminished, it is then necessary to pump the crude oil to the earth's surface. Oil wells are traditionally pumped using a sucker rod pump in which actuated by a string of sucker rods extending from the earth's surface. Vertical reciprocation causes constant reversal of stresses in an oil well pumping system resulting in fairly high wear rates. Further, when a well is exceptionally deep, such as 5,000 ft. or greater, problems associated with reciprocating sucker rods are greatly intensified.
One system that has been developed to produce crude oil from a deep well is by the use of hydraulically actuated pumps. The most common type of hydraulically actuated positive displacement down hole pumps employ pressure fluid that flows co-mingled back to the earth's surface with the production fluid. In some installations a separate return line is employed so that the hydraulic fluid employed for pumping action is re-circulated back to the earth's surface independently of the production fluid. However this system required parallel hydraulically operated fluid lines in addition to the production fluid passageway and the installation of this latter type of pump is more difficult. Therefore, the most common way of actuating a down hole hydraulically actuated pump utilizes the arrangement wherein power fluid is forced down central tubing to actuate a reciprocating pump engine to force production fluid into an annular area between the interior of a casing and the exterior of power tubing to the earth's surface and in which the spent power fluid is co-mingled with the production fluid. This system requires only concentric piping that is substantially easier to install and remove than parallel piping.
A typical hydraulically actuated downhole pump has a fluid powered motor, or ‘engine’, that produces reciprocal action and a reciprocating pump with a motor piston and a pump piston in axial alignment and connected by a piston rod. A typical pump is in the order of about 1.9 inches to 3.8 inches in diameter and from about 6.5 ft. to 25 ft. or longer and is positioned in a bottom hole assembly of a well casing. A well casing is typically in the order of about 4½ inches to 9 inches in diameter and the tubing used to supply high-pressure hydraulic fluid to actuate the pump may typically be from about 1½ inches to 3½ inches in diameter. As stated above, commingled power fluid and production fluid flows back to the earth's surface in the annual area between the interior of the casing and the exterior of the tubing.
A basic description of the operation and function of a bottom hole hydraulically actuated pump can be obtained from U.S. Pat. No. 2,081,223 entitled “Fluid Operated Deep Well Pump” that issued on May 25, 1937. This patent shows that hydraulically actuated downhole pumps have been known for at least 60 years.
Hydraulically actuated pumps must be removed periodically from a well for repair of worn parts and replacement of seals. The life of a hydraulically actuated pump depends upon many factors, a primary one being the nature of the fluid being handled, that is, whether the fluid is inherently corrosive and also upon where the production fluid carries entrained abrasive components, such as sand. Systems have been developed wherein the pump can be removed from a bottom hole location by the application of hydraulic fluid pressure. This eliminates the need for inserting a retrieval tool into the power fluid supply tubing for attachment to the upper end of the hydraulically actuated pump to physically remove the pump. The pump of the present disclosure is particularly adaptable for hydraulic removal. To remove a pump hydraulically, such as the pump described herein. fluid pressure is imposed in the annulus area, that is within the casing and exterior of the power supply tubing so that pressure is applied below the pump to force the pump upwardly within the power supply tubing to the earth's surface.
In order to obtain more pumping power, especially for operations at greater depths, multiple engine pumps have been developed. For an example of a multi-engine pump reference may be had to U.S. Pat. No. 3,653,786 entitled “Fluid Operated Pump Assembly With Tandem Engine” issued Apr. 4, 1972. In a pump of this design two fluid operated motors are positioned in tandem, one above the other with the motor pistons connected by an axial in-line piston rod. Some dual engine configurations require porting to the exterior of the pump to provide fluid paths around various components while other multi-engine pumps use internally ported arrangements. While the invention herein is described as it is applied to a single piston engine the invention can be combined with multiple engine or multiple pump systems.
For more background information reference may be had to the following previously issued United States patents:
U.S.Pat. No.INVENTORTITLE2,081,223C. J. CoberlyFluid Operated Deep Well Pump2,631,541O. E. DempseyHydraulic Pump2,787,961R. L. ChenaultSubsurface Hydraulic Pump Installation2,921,531J. R. Brennan,Pressure Fluid-Operated Pump Structureet al.2,949,857C. J. CoberlyFluid Operated Pump With SeparateEngine Valve3,109,379C. L. EnglishSubsurface Pump3,118,382C. L. EnglishSubsurface Pumping Unit3,374,746R. L. ChenaultHydraulically Operated Subsurface MotorAnd Pump Combination3,502,028R. F. CooperHydraulic Motor And Pump3,653,786R. F. McArthur,Fluid Operated Pump Assembly Withet al.Tandem Engines3,865,516G. K. RoederFluid Actuated Down-Hole Pump4,076,458R. L. JonesAutomatic Pump Speed Controller4,202,656G. K. RoederDownhole Hydraulically Actuated PumpWith Jet Boost4,406,598J. R. WallingLong Stroke, Double Acting Pump4,544,335G. K. RoederPiston and Valve Assembly4,768,589G. K. RoederDownhole Hydraulic Actuated Pump4,925,374D. E. CarrensDown Hole Hydraulically Actuated Pump5,104,296G. K. RoederEngine End For A DownholeHydraulically Actuated Pump Assembly5,209,651J. M. Kelleher,Multiple Engine Deep Well Pumpet al.5,494,102W. H. SchulteDownhole Hydraulically Operated FluidPump5,651,664A. C. Hinds,“Free” Coil Tubing Downhole Jetet al.Pump Apparatus And Method5,667,364D. P. O Mara,Downhole Hydraulic Pump Apparatuset al.Having A “Free” Jet Pump And SafetyValve Assembly And Method